1. Field of the Invention
The present invention relates to a multimedia communication terminal and, more particularly, to an improved video encoding/decoding apparatus and method for the multimedia communication terminal.
2. Background of the Related Art
Recently, the development and commercialization of IMT-2000 services multimedia handsets for simultaneously transmitting audio and video information through wired or wireless channels has increased.
In a multiplexed transmission system, the audio and video information should be encoded to maintain balance of the audio and video information. However, video information occupies a large amount of the whole data set to be transmitted, in comparison with audio information. Typically, the audio and video information is separately coded and transmitted through separate channels. Also, there is a method using one transmission channel for both the audio and video information. In this case, the encoding/decoding algorithm becomes complex for calculating the video information delay time which is used to synchronize the audio and video information.
Generally, the end-to-end delay of the video information in multimedia communication is 200˜400 ms (total allowable delay is 400 ms in H.324 and 3G-324
Generally, the end-to-end delay of the video information in multimedia communication is 200˜400 ms (total allowable delay is 400 ms in H.324 and 3G-324 standards). This delay time causes the video to appear choppy and also is much greater than that of the audio information, which is 30˜60 ms. The delay difference between the video information and the audio information contributes to the degradation of the multimedia communication quality. Accordingly, to synchronize the video information with the audio information, the audio information should be delayed as much as the delay difference between the audio and video information. In order to delay the audio information as much as the delay difference, a memory buffer is required for temporary storing the audio information, and the greater the delay difference is, the greater the memory buffer size required. The total delay can be divided into a propagation delay and a processing delay caused at the codec. However, since the delay caused by the channel is relatively stationary, it is critical to reduce the processing delay caused at the codec.
In the related art video codec, which may be implemented in hardware as well as software, the video information delay includes a processing delay of about 200˜400 ms. Even though these delay levels satisfy the H.321 and the 3G-324 standard recommendations, choppy movement on the motion picture caused by the delay makes users feel uncomfortable and adversely affects picture quality. Also, since the difference between the video and audio delays is great and varies, it is difficult to precisely synchronize the audio information with the video information.
Furthermore, in the related art codec, since the audio information should be stored so as to be synchronized with the video information which is much delayed, the need for additional memory resources for storing the audio information is an inevitable design consequence.